The Comers were sentenced to 30 years, with at least 15 years to be served in prison.
Paulding District Attorney Dick Donovan said the plea halts what could have been a future trial in which the Comers' two other children would have been forced to take the stand and relive the events leading up to the charges.
"If you were one of the girls who hadn't seen her brother, it would be a not-pleasant thing to go through," he said.
"We managed to get a good plea with significant jail time," Donovan said.
Son Mitch Comer, now 18, was found in September in a Los Angeles, Calif., bus terminal by a security guard. He later told police investigators he had been locked in his darkened bedroom and barely fed for years before Paul Comer, his stepfather, put him on a bus and told him to find a homeless shelter.
Comer reportedly weighed just 87 pounds at the time.
The boy reportedly is now living in foster care.
Donovan said someone from his office will be at any upcoming probation or parole hearings for the Comers to remind about the events leading up to the charges.
The plea also results in the Comers forfeiting all their assets to go into a trust fund for their children.
"I hope it shows the community we care about the victims in our cases," he said.